Implantable cardiac stimulation devices, such as pacemakers and cardiovertor defibrillators, generally rely on cardiac electrogram (EGM) signals for determining a cardiac rhythm and delivering stimulation therapies as needed.
For example, R-waves are sensed from EGM signals for detecting R-R intervals which are used in detecting and classifying a number of arrhythmias, including ventricular fibrillation (VF) and tachycardia. Oversensing of other cardiac or non-cardiac signals is avoided. Automatic threshold adjustments or increased blanking intervals can be used for preventing oversensing of T-waves, which follow R-waves and are typically lower in amplitude. It is desirable to prevent T-wave oversensing from reducing the sensitivity and accuracy of rhythm detection based on R-wave sensing.